Geoengineering Large Ensemble Project (GLENS)

The Stratospheric Aerosol Geoengineering Large Ensemble project is a 20-member ensemble of stratospheric sulfate aerosol geoengineering simulations between 2020-2099 and a 20-member ensemble of control simulations over a reference period between 2010-2030 using the NCAR Community Earth System Model with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM1 WACCM) described in Mills et al., 2017. The goal of the geoengineering simulations was to maintain not only global mean surface temperature, but also interhemispheric and equator-to-pole surface temperature gradients at 2020 values under a RCP8.5 greenhouse gas scenario. To reach these climate objectives, a feedback-control strategy was employed to manage uncertainty and variability in the climate system by optimizing annual injections at four different locations in the stratosphere, namely at 30°N, 30°S, 15°N and 15°S. This feedback strategy was developed based on several independent single point sulfur injection experiments aimed at identifying the relationships between injection location and surface temperature response (Tilmes et al., 2017, MacMartin et al., 2017, Richter et al., 2017), which was then applied to a single-member simulation (Kravitz et al., 2017). The Stratospheric Aerosol Geoengineering Large Ensemble has been performed the same way as the earlier single-member simulation, only using a newer version of the land model than in Kravitz et al. (2017). The results of these simulations can be used to identify robust regional and seasonal climate change, extremes, and variability as the result of strategically performed geoengineering and to identify reasonable limits of stratospheric aerosol engineering. We hope for large community involvement in analyzing these experiments.

Both control and geoengineering simulations follow the same RCP8.5 pathway. The control simulations were performed over the reference period between 2010 and 2030. Three of these members were continued through at least 2097. The geoengineering simulations were branched from each of the 20 control simulations in 2020. Sulfur injections using the feedback-control algorithm were applied to each of the 20 members separately to keep the global temperature and hemispheric temperature gradients at 2020 conditions. All 20 members of these simulations continued until 2099. Further details of the simulations are described in Tilmes et al. (2018).

All the data from these simulations are available to the community which can be found in the sidebar links of this page.

Project Team


  • 2017

  • Kravitz. B., D. G. MacMartin, M. J. Mills, J. H. Richter, S. Tilmes, J. F. Lamarque, J. J. Tribbia, and F. Vitt (2017) First simulations of designing stratospheric sulfate aerosol geoengineering to meet multiple simultaneous climate objectives, JGR-Atmospheres ]
  • MacMartin D. B., B. Kravitz, S. Tilmes, J. H. Richter, M. J. Mills, J. F Lamarque, J. J. Tribbia, and F. Vitt (2017) The climate response to stratospheric aerosol geoengineering can be tailored using multiple injection locations, JGR-Atmospheres ]
  • Mills M. J. , J. H. Richter, S. Tilmes, B. Kravitz, D. MacMartin, S. Glanville, A. Schmidt, J. J. Tribbia, A. Gettelman, C. Hannay, J. T. Bacmeister, D. E. Kinnison, F. Vitt, and J. F. Lamarque (2017) Radiative and chemical response to interactive stratospheric aerosols in fully coupled CESM1(WACCM), JGR-Atmospheres ]
  • Richter J. H., S. Tilmes, M. J. Mills, J. J. Tribbia, B. Kravitz, D.G. MacMartin, F. Vitt and J. F. Lamarque (2017) Stratospheric Dynamical Response to SO2 Injection, JGR-Atmospheres ]
  • Tilmes, S., J. H. Richter, M. J. Mills, B. Kravitz, D.G. MacMartin, F. Vitt, J. J. Tribbia, and J. F. Lamarque (2017) Sensitivity of aerosol distribution and climate response to stratospheric SO2 injection locations, JGR-Atmospheres ]
  • 2018

  • Fasullo, John T. and Tilmes, Simone and Richter, Jadwiga H. and Kravitz, Ben and MacMartin, Douglas G. and Mills, Michael J. and Simpson, Isla R. (2018) Persistent polar ocean warming in a strategically geoengineered climate, Nature Geoscience ]
  • Kravitz, B., MacMartin, D. G., Tilmes, S., Richter, J. H., Mills, M. J., Lamarque, J.‐F., Tribbia, J., & Large, W. (2018) Holistic assessment of SO2 injections using CESM1(WACCM): Introduction to the special issue. Journal of Geophysical Research: Atmospheres, 123. ]
  • Richter, J. H., Tilmes, S., Glanville, A., Kravitz, B., MacMartin, D. G., Mills, M. J., et al. (2018) Stratospheric response in the first geoengineering simulation meeting multiple surface climate objectives. Journal of Geophysical Research: Atmospheres, 123, 5762–5782 ]
  • Sasha Madronich, Simone Tilmes, Ben Kravitz, Douglas G. MacMartin and Jadwiga H. Richter (2018) Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO2 Injections Atmosphere. 9(11), 432; ]
  • Tilmes, S., Richter, J. H., Mills, M. J., Kravitz, B., MacMartin, D. G., Garcia, R. R., et al. (2018) Effects of different stratospheric SO2 injection altitudes on stratospheric chemistry and dynamics. Journal of Geophysical Research: Atmospheres, 123, 4654–4673 ]
  • Tilmes, S., J.H. Richter, B. Kravitz, D.G. MacMartin, M.J. Mills, I.R. Simpson, A.S. Glanville, J.T. Fasullo, A.S. Phillips, J. Lamarque, J. Tribbia, J. Edwards, S. Mickelson, and S. Gosh (2018) CESM1(WACCM) Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) Project. Bull. Amer. Meteor. Soc., 0 ]
  • 2019

  • MacMartin, D.G, W. Wang, B. Kravitz, S. Tilmes, J.H. Richter, and M.J. Mills. (2019) Timescale for detecting the climate response to stratospheric aerosol geoengineering, J. Geophys. Res. Atmos., 124. ]
  • Jiang, J., Cao, L., MacMartin, D.G., Simpson, I.R., Kravitz, B., Cheng, W., Visioni, D., Tilmes, S., Richter, J.H. and Mills, M.J. (2019) Stratospheric sulfate aerosol geoengineering could alter the high‐latitude seasonal cycle. Geophysical Research Letters, 46(23), pp.14153-14163
  • Kravitz, B. (2019) Managing uncertainties in climate engineering, Eos, 100 ] Published on 23 January 2019
  • Kravitz, B., MacMartin, D. G., Tilmes, S., Richter, J. H., Mills, M. J., Cheng, W., et al. (2019) Comparing surface and stratospheric impacts of geoengineering with different SO2 injection strategies. Journal of Geophysical Research: Atmospheres, 124. ]
  • Visioni, D., D.G. MacMartin, B. Kravitz, S. Tilmes, M.J. Mills, J.H. Richter, and M.P. Boudreau (2019) Seasonal injection strategies for stratospheric aerosol geoengineering. Geophysical Research Letters, 46, 7790– 7799. ]
  • D. Visioni et al. Changes in sulfate geoengineering efficacy due to uncertainties in model representations of high clouds, JGR, in revision
  • Cheng, W., D.G. MacMartin, K. Dagon, B. Kravitz, S. Tilmes, J.H. Richter, M.J. Mills, I.R. Simpson (2019) Soil moisture and other hydrological changes in a stratospheric aerosol geoengineering large ensemble, J. Geophysical Research A. 124. ]
  • Xia L., Robock A., S. Tilmes, M. J. Mills, J. H. Richter, B. Kravitz, D. MacMartin, D. Visioni. Impacts of Sulfate Injection Geoengineering on Particulate Matter with Diameter less than 2.5 µm, submitted to ACP
  • Simpson, I. R., Tilmes, S., Richter, J. H., Kravitz, B., MacMartin, D. G., Mills, M. J., et al. (2019) The regional hydroclimate response to stratospheric sulfate geoengineering and the role of stratospheric heating. Journal of Geophysical Research: Atmospheres, 124, 12587–12616 ]
  • 2020

  • Banerjee, A., Butler, A. H., Polvani, L. M., Robock, A., Simpson, I. R., Sun, L. (2020) Robust winter warming over Eurasia under stratospheric sulfate geoengineering – the role of stratospheric dynamics, Atmos. Chem. Phys. Discuss. ] Preprint in review
  • Da‐Allada, C. Y., Baloïtcha, E., Alamou, E. A., Awo, F. M., Bonou, F., Pomalegni, Y., et al. (2020) Changes in west African summer monsoon precipitation under stratospheric aerosol geoengineering. Earth's Future, 8, e2020EF001595. ]
  • Irvine, P.J. and Keith, D.W. (2020) Halving warming with stratospheric aerosol geoengineering moderates policy-relevant climate hazards. Environmental Research Letters, 15(4), p.044011
  • Karami, K., Tilmes, S., Muri, H., & Mousavi, S. V. (2020) Storm track changes in the Middle East and North Africa under stratospheric aerosol geoengineering. Geophysical Research Letters, 47, e2020GL086954. ]
  • Lee, W., MacMartin, D., Visioni, D., and Kravitz, B.: Expanding the design space of stratospheric aerosol geoengineering to include precipitation-based objectives and explore trade-offs, Earth Syst. Dynam., 11, 1051–1072 ]
  • Odoulami, R.C., New, M., Wolski, P., Guillemet, G., Pinto, I., Lennard, C., Muri, H. and Tilmes, S. (2020) Stratospheric Aerosol Geoengineering could lower future risk of ‘Day Zero’level droughts in Cape Town. Environmental Research Letters, 15(12), p.124007 ]
  • Pinto, I., Jack, C., Lennard, C., Tilmes, S., & Odoulami, R. C. (2020) Africa's climate response to solar radiation management with stratospheric aerosol. Geophysical Research Letters, 47, e2019GL086047. ]
  • Visioni, D., MacMartin, D. G., Kravitz, B., Richter, J. H., Tilmes, S., & Mills, M. J. (2020) Seasonally modulated stratospheric aerosol geoengineering alters the climate outcomes. Geophysical Research Letters, 47, e2020GL088337. ]
  • Visioni, D., Isla Ruth Simpson, Douglas G MacMartin, Jadwiga H. Richter, Ben Kravitz, Walker Lee (2020) Reduced poleward transport due to stratospheric heating under geoengineering ]
  • Visioni, D., E. Slessarev, D.G. MacMartin, N.M. Mahowald, C.L. Goodale, and L. Xia (2020) What goes up must come down: impacts of deposition in a sulfate geoengineering scenario, Environmental Research Letters. ]
  • Xu, Y., Lin, L., Tilmes, S., Dagon, K., Xia, L., Diao, C., Cheng, W., Wang, Z., Simpson, I., Burnell, L. (2020) Climate engineering to mitigate the projected 21st-century terrestrial drying of the Americas: a direct comparison of carbon capture and sulfur injection, Earth Syst. Dynam., 11, 673–695 ]
  • Yang, C.-E., F. M. Hoffman, D. M. Ricciuto, S. Tilmes, L. Xia, D. G. MacMartin, J. H. Richter, M. Mills, B. Kravitz, and J. S. Fu (2020) Assessing terrestrial biogeochemical feedbacks in a strategically geoengineered climate, to appear, ERL.
  • 2021

  • Robrecht, S., Vogel, B., Tilmes, S. and Müller, R. (2021) Potential of future stratospheric ozone loss in the midlatitudes under global warming and sulfate geoengineering. Atmospheric Chemistry and Physics, 21(4), pp.2427-2455